1. Field of the Invention
This invention relates to a vacuum operation apparatus and, more particularly, to a vacuum operation apparatus which can set a desired vacuum pressure and residence time for each operation and can cope with various operating conditions.
2. Description of the Prior Art
A vacuum operation process such as CVD (Chemical Vapor Deposition) or dry etching is used in film formation operation and lithography operation in a semiconductor device manufacturing process. In this vacuum operation process, for example, a wafer is placed in an airtight operation chamber, and the operation chamber is evacuated by a vacuum exhaust pump. Then, a reaction gas is supplied to perform an operation such as CVD or etching using plasma ions produced by RF power, radicals (neutral active species), or the heat of a heater.
The schematic structure of a vacuum operation apparatus for executing a vacuum operation process will be described with reference to FIGS. 1A and 1B.
The vacuum operation apparatus shown in FIGS. 1A and 1B is constituted by a chamber 30, an exhaust pipe 31 connected to the chamber 30, a pressure control orifice 33 which is disposed in the exhaust pipe 31 to control the pressure in the chamber 30, and a focus ring 36 which surrounds a wafer 35 placed on a wafer support 34 in the chamber 30, focuses an etching species such as plasma ions on the operation surface of the wafer, and achieves a desired residence time on the wafer operation surface.
A reaction gas for performing an operation such as etching for a wafer is supplied to the chamber 30. The pressure in the chamber 30 is controlled to be suitable for conditions for each operation by adjusting the opening degree of the pressure control orifice 33.
The diameters of the chamber 30, exhaust pipe 31, and focus ring 36 are designed in accordance with process conditions used so as to optimize the residence time.
For example, when the exhaust pipe 31 is relatively thin with respect to the chamber capacity, the vacuum degree in the chamber 30 is generally low (pressure is high), and the amount of gas flowing from the chamber 30 to the exhaust pipe 31 is small. Such a vacuum operation apparatus with a narrow exhaust port is suitable for an operation at high pressure and little flow rate. The residence time is designed to eliminate any wafer in-plane difference of etching under the conditions of this apparatus.
When the exhaust pipe 31 is relatively thick with respect to the chamber capacity, the vacuum degree in the chamber 30 can be increased (pressure can be decreased), and the amount of gas flowing from the chamber 30 to the exhaust pipe 31 is large. Such a vacuum operation apparatus with a wide exhaust port is suitable for an operation at low pressure and great flow rate. The residence time is designed to eliminate any wafer in-plane difference of etching under the conditions of this apparatus.
In this manner, the conventional vacuum operation apparatus must be designed in consideration of the pressure, flow rate, and residence time for each operating condition. It is difficult to design, maintain, and manage the vacuum operation apparatus. Also, the cost becomes high.
If a vacuum operation apparatus optimally designed for specific operating conditions is used for an operation under different operating conditions, desired operation performance cannot be obtained. An operation in-plane difference occurs on a wafer, which inhibits proper execution of an operation.
The present invention has been made in consideration of the conventional situation, and has as its object to provide a vacuum operation apparatus capable of performing various operations in one chamber, realizing an appropriate residence time corresponding to each operation, and obtaining desired operation performance.
To achieve the above object, according to the first aspect of the present invention, there is provided a vacuum operation apparatus comprising a chamber for operating a wafer at a predetermined vacuum pressure, an exhaust pipe connected to the chamber to connect the chamber to exhaust means for evacuating the chamber, a pressure control orifice disposed in the exhaust pipe to control a pressure in the chamber, and a residence time control variable orifice which is disposed in the exhaust pipe separately from the pressure control orifice, and opened/closed independently of the pressure control orifice to control the residence time of gas in the vacuum chamber.
According to the first aspect, the residence time control variable orifice can control the exhaust flow rate, and can adjust the residence time in the chamber to be suitable for desired operating conditions. The pressure control orifice can perform fine adjustment for keeping the interior of the chamber at a preset pressure. The residence time control variable orifice and pressure control orifice are separately arranged, and independently opened/closed. Hence, the two steps can be independently done.
This arrangement can set the interior of the chamber to a desired operation state, and can adjust the residence time to a desired value.
The vacuum operation apparatus according to the first aspect comprises pressure measurement means for measuring the pressure in the chamber. The opening degree of the pressure control orifice is controlled in accordance with a measurement value detected by the pressure measurement means, and the residence time control variable orifice is set to an opening degree corresponding to an operation executed in the chamber.
The pressure control orifice is disposed on the exhaust channel of the exhaust pipe, and the residence time control variable orifice is disposed in the exhaust pipe between the chamber and the pressure control orifice. The residence time control variable orifice includes a slide type valve disposed along the outer wall of the chamber.
According to the second aspect of the present invention, there is provided a vacuum operation apparatus in which a semiconductor wafer is placed in a chamber, a reaction gas is supplied to the chamber, and the semiconductor wafer undergoes vacuum operation while a pressure control orifice disposed in an exhaust pipe connected to the chamber controls a pressure in the chamber, comprising a residence time control variable orifice which is opened/closed independently of the pressure control orifice to control the residence time of gas in the chamber, wherein the pressure in the chamber and the residence time can be controlled independently of each other.
According to the second aspect, various operations can be executed in one chamber, and a desired residence time can be realized for each operation. As a result, desired operation performance can be obtained.
The above and many other objects, features and advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which preferred embodiments incorporating the principle of the present invention are shown by way of illustrative examples.